Dead-end filtration of natural organic matter: experimental evidence of critical conditions

The development of membrane technology has reached a state whereby operational optimisation is becoming the major issue to both researchers and industrial operators. A key focus is towards sustainable operation where fouling is limited and cleaning is greatly reduced. The paper presents an example of such an approach for the filtration of natural organic matter (NOM) in a dead-end ultrafiltration cell. Sustainable operation has been assessed in relation to the application of a cessation period followed by a gentle rinse. The work demonstrates the existence of a critical filtered volume below which the mass accumulated at the membrane’s surface is reversible and above which significant fouling occurs. Further, appropriate selection of operating conditions (filtered volume and applied pressure) makes it possible to avoid the formation of an irreversible fouling layer.

The results indicate that for a given pressure there exists an associated critical filtered volume, below which fouling is reversible by rinsing whereas above this critical filtered volume a significant part of fouling is irreversible. The effect of the relaxation time before rinsing on the irreversibility was demonstrated to increase the degree of reversibility attainable. The recovery in flux was found to be strongly linked to the operating pressure. The critical fouling conditions, defining a critical change in fouling irreversibility, seem to relate to the combination of operating conditions: applied pressure/filtered volume.